Realistic Material viewport without rendering?
You will not be able to have real: transparent raytracing, mirroring, subsurface scattering, generated texture coordinates, multiple light bounces

Set the 3D View Shading to Material. In the Display section of the Properties Panel check "Only Render" and "World Background". In the Shading section select GLSL shading and check ambient occlusion.

In the Viewport you can use the Blender Game Shaders / Lights.

Utilize Texture baking all Textures Channels except Specular/Glossy.

There are many different techniques to fake rendering effects.

I advise you to check out these two tutorials:


Viewport Rendering: Blender Game Engine Material
Hacking The Viewport: Many Hacks and Fake Effects


EDIT: Jerryno's comment suggests PBR, which is an important resource as well.